Relaxation time changes of the uterus during the menstrual cycle: correlation with hormonal status

Six women volunteers underwent pelvic MR imaging at 0.02 T four times during their menstrual cycle. The T1 and T2 relaxation times of the myometrium and endometrium were measured and correlated with the serum estradiol and progesterone levels. The magnitude of the relaxation times were highly individual but the pattern of their variation during the menstrual cycle was similar. The relaxation times were shortest at the beginning and end of the cycle. The most rapid increase occurred during the proliferative phase, followed by little or no increase through to the middle of the secretory phase. The T1 and T2 times of the endometrium correlated directly with the serum estradiol levels during the entire menstrual cycle (r = 0.5, P = 0.02) and the T2 times of the endometrium with the serum progesterone levels during the secretory phase (r = 0.6, P = 0.05). The correlation between the relaxation times of the myometrium and the serum hormonal levels was poor. The results indicate that the relaxation times of the myometrium and endometrium vary during the menstrual cycle reflecting the serum hormonal status. MR imaging of the uterus with relaxation time measurements may be clinically useful to examine the menstrual cycle and its pathology.